I have a Zen27 with the 2.3 V firmware and the built in Hubitat "Zooz Central Scene Dimmer" driver.
I just finished a RM allowing me to control my garage flood light from the front entrance switch using double tap.
When testing I found an inconsistent behavior and was wondering if this was intentional.
Double taping the top (ON) of the paddle both the Garage Flood turns ON (via RM rule) AND the Front entrance light turns ON (direct wired to Zen 27)
When I double tap the bottom of the paddle, the garage flood goes OFF (again via the RM rule) but the Front entrance (wired to the Zen) stays ON. If it were consistent I would expect the light to go OFF with the double tap.
In general I was under the assumption the double tap would be ignored by the wired light.
Since they are both exterior lights at the front of the house it is not a big deal. But I would like to know if it by design and/or changeable.
Certain multi-taps are indeed special in some cases on the ZEN27 (and ZEN26 and possibly others), so the behavior you're seeing is actually expected. Here's their marketing material that explains the behavior for multi-taps on this device, including the 2x up feature you noticed::
Further, according to the manual, I don't see a way to disable that feature for double-tap up* (just a way to specify the maximum brightness for everything, including this). I see you've tagged Zooz and am sure they will know if this has changed recently--or consider it a feature request if not.
(*EDIT: apparently, there is indeed a setting to disable this; see below -- and of course, if you just wanted a double tap down to also turn off the light, that is easily do-able with a hub-side automation if you're OK with the onboard "up" behavior)
I just checked a couple of my button controller. It seems like with scene control enabled the double tap up behaviour is determined by parameters 12 and 14 but double tap off does not turn off the light automatically.
@JohnRob The dimmer is programmed by default to turn the light on to full brightness with double tap up. Double tap down is not pre-programmed to turn the light off since you can do that with just a single tap down If you don't need the double tap for instant full brightness, you can disable the double tap feature as @steve.maddigan suggested and use it for scene control only. Hope that helps!
If you don't need the double tap for instant full brightness, you can disable the double tap feature as 
